1. Field of the Invention
The present invention is directed to water-dispersible, electrolyte-stable polyetherester-modified polyurethane ionomers, a process for their production and their use in combination with polymers containing perfluoroalkyl groups as hydrophobizing and oleophobizing agents for textiles.
2. Description of the Prior Art
High quality aqueous dispersions of polyurethanes or polyurethane ureas are known and have been described, for example, in Angewandte Chemie, 82, (1970), pages 53 to 63; DE-OS 2,314,512; and 2,314,513.
The fact that many of these dispersions are free from external emulsifiers contributes to this high level. The dispersions contain chemically incorporated hydrophilic centers which are responsible for the self-emulsifiability of the otherwise hydrophobic polymers.
The hydrophilic centers incorporated in the known water-dispersible polyurethanes or polyurethane ureas include both salt-like, i.e. ionic groups and hydrophilic, nonionic groups.
The "polyurethane ionomers" include both polyurethanes containing chemically incorporated cations, in particular ammonium ions, and polyurethanes containing chemically incorporated anions, in particular sulfonate or carboxylate groups. The nonionic, water-dispersible polyurethanes include polyurethanes containing polyethylene oxide side chains according to DE-OS 2,314,512 and 2,314,513.
The dispersions of these polyurethanes have various characteristic property spectrums, depending on the nature of the hydrophilic center. Thus, because the solubility of the salt groups present in them is substantially independent of temperature, polyurethane ionomers dispersions will withstand heating to the boiling temperature; whereas, nonionic dispersions coagulate when heated to only moderate temperatures (approx. 60.degree. C.) because the polyethylene oxide side chains gradually lose their solubility in water at these temperatures. In contrast to ionomers, however, these dispersions are resistant to the addition of almost unlimited quantities of electrolytes and are also stable after freezing and thawing.
Sensitivity to electrolytes is particularly high in the case of cationic polyurethanes. Aqueous dispersions of polyurethanes containing quaternary ammonium or tertiary sulfonium groups coagulate immediately, even if only very small quantities of an electrolyte containing monovalent ions, such as sodium chloride, are added in aqueous solution. On account of this property, the production and application of cationic polyurethane dispersions involves particular problems. Thus, water substantially free from ions generally has to be used for their production. "Hard" water leads to an unwanted increase in the size of the dispersed particles or to partial coagulation.
It is known from DE-OS 2,551,094, DE-OS 2,651,505 and DE-OS 2,730,514 that the sensitivity of aqueous polyurethane ionomers to electrolytes can be drastically reduced by the use of polyethers containing terminal and/or lateral polyethylene oxide. However, the use of polyethylene oxide units incorporated in the polymer results in hydrophilic properties which are permanent and thus seriously restrict the use of such ionically/nonionically modified polyurethanes for many applications, for example, for the crease-resistant finishing of fabrics.
It has now surprisingly been found that the known unfavorable properties of nonionically stabilized polyurethane ionomer dispersions can be avoided by incorporation of certain polyether ester groups in the polyurethane ionomer.